Third-generation cephalosporin resistance in clinical isolate of Shigella sonnei in Andaman & Nicobar Islands, India

Diarrhoea is an important cause of morbidity and mortality in all regions of the world and among all ages [1]. It has been estimated that 91 million individuals worldwide contract shigellosis each year and among them 1.1 million die [2]. About, 410,000 (40%) of these deaths occur among Asian children [3]. Appropriate antibiotic treatment of shigellosis depends on identifying resistance patterns [4]. Rapid emergence of resistance warrants the need for continuous monitoring of sensitivity patterns [5]. The emergence of multiple-drug resistant (MDR) strains of Shigella sp., especially over the last two decades, has made the treatment for shigellosis more difficult. Currently ciprofloxacin (or other fluoroquinolones) is recommended as the drug of choice by the World Health Organization for the therapy of Shigella infections in both adults and children [6]. In addition, ceftriaxone, pivmecillinam (amdinocillin pivoxil) and azithromycin are considered as alternative drugs suitable for treatment of shigellosis [6]. Shigella species expressing extended-spectrum beta-lactamases (ESBLs) have emerged globally and this situation has limited the treatment strategies available for shigellosis. The archipelago of Andaman and Nicobar (92-94ºE; 6-14ºN), a chain of more than 500 islands situated about 1,200 km southeast of Indian peninsula in the Bay of Bengal, is a Union Territory of India. These islands are the home to 350,000 people including six indigenous tribes and settlers from mainland India. Health care is almost entirely provided by the government. G. B. Pant Hospital, located at Port Blair, the capital of the Union Territory, is the only referral hospital in the islands. Hospital-based bacteriological surveillance has identified shigellosis as endemic and a major cause of acute childhood diarrhoea [7,8] with S. flexneri 2a as the commonest isolate. A stool sample was collected from a male child aged one and half years who was admitted in G. B. Pant Hospital prior to the administration of antimicrobials. He was admitted with high-grade fever (for three days), vomiting, and severe watery stool with blood. The patient was initially treated with intravenous fluid and powergyl (metronidazole 500 mg, norfloxacin 400 mg/5 mL), to which he did not respond. The sample was processed following standard techniques [9]. S. sonnei was isolated on Hektoen Enteric Agar (Difco, Detroit, USA) and confirmed by biotyping and serotyping. Antibiotic susceptibility testing was conducted using the disc diffusion method, according to Clinical and Laboratory Standards Institute guidelines [9] using the following antibiotic discs (Hi-Media, Mumbai,